1. Field of the Invention
The present invention relates to a submember which is involved in an electrical device, more particularly, it relates to an submember mounted on a chip is for enhancing the reliability of electrical device, downsizing the electrical device and saving materials of electrical device.
2. Description of the Related Art
Nowadays, electrical devices are becoming more powerful than before, and users of electrical device are continually demanding better reliability of electrical devices, thinner electrical devices and inexpensive electrical devices, In this manner, manufacturers of electrical device research and develop the improved electrical devices for achieving the demands mentioned-above.
At first, referring to FIG. 22A, 22B (FIG. 22B is a cross-sectional view of FIG. 22A) show a conventional 100 comprising: a base 30 serving as a substrate includes a first surface 31, an opposing second surface 32, a receiving area 80 is for accommodating a chip, a plurality of conductive fingers 70, two power supply rings 91 for supplying different voltages such as 1.33V or 3.3V etc. to the chip 20, two power supply rings 92 for grounding, and a plurality of solder balls 50, wherein, the conductive fingers 70 surrounding the power supply rings 91 and the solder balls 50 attached on the second surface 32 of base 30, said solder balls 50 electrically connected the base 30 to the outside (such as a mother board etc.); a chip 20 mounted on the receiving area 80 of base 30; a plurality of conductive wires 60 electrically connected the chip 20 to the conductive fingers 70, the power supply rings 91,92 respectively; and an encapsulant encapsulates the chip 20, base 30 and the conductive wires 60; According to said conventional electrical device 100, due to the conductive fingers 70 surrounding the power supply rings 91, In this manner, the distance “A” between the chip 20 and the conductive finger 70 becomes the longest, then the conductive wires 60 which are electrically connected the chip 20 to the conductive fingers 70 also become the longest (because it is necessary for said conductive wires 60 to pass through the width “D”, “E” of power supply ring 91, 92.), As this result, more materials of conductive wire 60 are needed, wherein, the conductive wires 60 are made of gold usually; since more conductive wires 60 are used, then the cost will be higher, In addition, due to the power supply rings 91, 92 are all situated on the first surface 31 of base 30, wherein if the amount of said power supply rings 91, 92 are increased, then the amount of conductive finger 70 will be reduced, as it has been mentioned that “Electrical devices are becoming more powerful nowadays.” If the amount of conductive fingers 70 on the first surface 31 of base 30 is not enough sufficiently, then the function of electrical device 100 will be limited (due to the more powerful the electrical device 100 is, the more conductive fingers are needed.), Nevertheless, it is difficult to setup both of the increased-gradually conductive fingers and the power supply rings on the same surface of base 30 without changing the size of said base 30. Therefore, in order to solve the problems mentioned-above, an interconnecting mean such as a circuit board-an interconnecting apparatus or an interconnecting substrate etc. is used in an electrical device, as shown in FIGS. 23A, 23B and FIG. 24, (FIG. 23B is a cross-sectional view taken along the “A—A” line in FIG. 23A ); FIGS. 23A, 23B and FIG. 24 show the last two steps of manufacturing a conventional circuit board 4, Firstly, refer to FIG. 23A, 23B showing a conductive layer 9 consists of a plurality of circuits 9k, 9m, wherein the circuits 9k, 9m connect to each other by means of the traces 2 respectively, said conductive layer 9 formed on said insulating layer 5, wherein a conductive material(s) (not shown) such as nickel, gold, palladium, silver or the like is(are) coated on the conductive layer 9 by means of a plating process for enhancing the quality of electrical connection (i.e. the reliability that the conductive layer 9 electrically connect to the conductive wires enables to be enhanced.) In addition, the conductive layer 9 is a predetermined shape (i.e. strip or the like) for easier operating the plating process and the mass production; Secondly, FIG. 24 shows After plating process, providing a blade “B” for sawing both the conductive layer 9 and the insulating layer 5, and then a circuit board 4 is accomplished, Nevertheless, due to the conductive layer 9 (i.e. the circuits 9k, 9m) is formed on the insulating layer 5, It is easy for the portion 9a of conductive layer 9 which is immediately adjacent to the blade “B” to be peeling off the insulating layer 5 while operating the sawing process. Should such a peeling-off problem occur, the reliability of said circuit board 4 will become poor. wherein although an insulating film such as a solder mask (not shown) can be provided upon the insulating layer 4 and a portion of the conductive layer 9 for protecting the circuit board 4, However the cost is increased, moreover, the risk of said peeling-off problem is still there, because the sawing process is needed to be operating; As shown in FIG. 25, wherein the conventional circuit board 4 manufactured by the method mentioned in FIGS. 23A, 23B and FIG. 24 is mounted on the chip 20, said circuit board 4 includes an insulating layer 5 which is selectively made by a fiber glass, epoxy, ceramics, silicon etc. and a conductive layer 9 which consists a plurality of circuits 9k, 9m and is served as power/ground ring; a plurality of conductive wires 60 electrically connected the chip 20 among the circuit board 4 and the base 30; due to the power rings have already been moved onto the circuit board 4, then there is not any power ring on the base 30, and then the conductive wires 60 which are electrically connected the chip 20 to the base 30 enable to be shortened (due to the conductive wires 60 electrically connected the chip 20 to the conductive fingers 70 are not needed to pass over the width “D”, “E” of power rings 9k, 9m, then the distance “A” between said chip 20 and said conductive finger 70 becomes shortened), and then the material of said conductive wires 60 enable to be saved; Nevertheless due to the conductive layer 9 is formed on the insulating layer 5 of circuit board 4, and the more serious problems caused by the peeling-off problem described in FIG. 24 will be happened by means of thermal effects (stress), Detailed descriptions as follows.
Due to the chip 20 generates heat while operating, then the thermal stress starts to affect the chip 20, the insulating layer 5, the conductive layer 9, the conductive wires 60, the base 30, the solder balls 50 and the encapsulant 40 respectively, during the period of thermal effects; wherein because the coefficient of thermal expansion of each part (i.e. the chip 20, the insulating layer 5, the conductive layer 9, the conductive wire 60, the base 30, the solder ball 50 and the encapsulant 40) is different from each other, then the thermal effects will be more serious to each part. In this manner, If the portion (see “9a” in FIG. 24) of the conductive layer 9 is separated from the insulating layer 5 at first, then said portion (9a) will be moving, and then the other portion of conductive layer 9 which is connected to the portion (9a) will be separated from the insulating layer 5 gradually (i.e. the more the portion (9a) is moving, the more the portion of conductive layer 9 will be separated from the insulating layer 5), eventually, once the portion of conductive layer 9 which is electrically connected to the end of conductive wire 60 is also separated from the insulating layer 5 and starts moving, then said end of conductive wire 60 which is electrically connected to the conductive layer 9 will be separated from the conductive layer 9 and/or the conductive wire 60 which is electrically connected the chip 20 to the conductive layer 9 will be broken by means of the thermal stress, in this manner, the electrical device 100 will be damaged or not functional well, then the reliability of said electrical device 100 becomes poor; Furthermore, due to the conductive layer 9 is formed on the insulating layer 5, then (i). the thickness of said circuit board 4 is thicker; and (ii). the material of insulating layer 5 needs to be used more.